Last Thursday, Senate Republicans failed in their third bid to block the nuclear deal with Iran. Signed in July, the agreement between Iran, the United States, and the five other PN+1 countries gradually eases economic sanctions on Iran in return for strict controls on that country’s nuclear-weapons program.

Virtually all of the debate surrounding the agreement has focused on the political and economic scorecard. Obama wins, as does the Iranian economy; hawks, in the United States and Iran, lose. Behind the scenes, though, a number of participants are also claiming a quieter victory for scientists.

Scientists have been involved in the international politics of atomic weapons since the fall of 1945, when veterans of the Manhattan Project, led by the physicist J. Robert Oppenheimer, attempted to convince the U.S. government that world security depended on the international control of fissile materials. In the 1950s and 1960s, U.S. policymakers experimented with a more formal role for scientists in international relations, installing science attachés and technical advisors in key embassies. Sometimes as private citizens, and sometimes as government officials, American scientists participated in the negotiations that produced the Antarctic Treaty of 1959, the Partial Test Ban Treaty of 1963, the Strategic Arms Limitation Treaty (SALT I) of 1972, and many more.

The popularity of “science diplomacy” has waxed and waned, but the U.S. Secretary of Energy Ernest Moniz’s role in promoting the Iran deal surely heralds its return. In practice, science diplomacy can mean any number of things: Scientists might serve as technical advisors to a government agency with international responsibility, or they might participate directly in negotiations. But because scientists routinely cross international borders to attend conferences and  to work with foreign colleagues, science diplomacy also has a more informal mode, something more akin to “building fellow feeling.” Think of American astronauts exchanging “handshakes in space” with their Soviet counterparts after docking their Apollo and Soyuz capsules in July 1975.

Since 1950, when a report by the physicist Lloyd Berkner urged the State Department to incorporate science into its regular operations, the concept of science diplomacy has mixed an optimism associated with the most idealized visions of scientific behavior with raw cynicism about scientists’ access to people and information. At the moment, optimism is ascendant, thanks in no small part to the role of scientists in the nuclear negotiations.

This spring, several reports noted the odd, and yet somehow inevitable, coupling of Secretary Moniz and Ali Akbar Salehi, the head of Iran’s Atomic Energy Organization. The two men both spent time at the Massachusetts Institute of Technology in the 1970s: Moniz as member of the physics faculty, Salehi as a graduate student in nuclear engineering. Although their paths didn’t cross in Cambridge, they shared the language of science and mutual acquaintances. By late March of this year, Moniz and Salehi were on a first-name basis, “disappearing for hours at a time,” according to The New York Times, to discuss centrifuges and plutonium production.

Richard Stone, the international editor for Science magazine, credits the scientists’ participation with “getting the negotiations back on track.” Stone has been covering science in Iran since 2005, and has recently interviewed Ali Salehi.

In the interview, Salehi makes bold claims not only for the importance of technical expertise at the negotiating table, but also for being able to communicate with Moniz, scientist-to-scientist. As he told Stone, “We tried to be logical and fair. We understood each other.” Their national commitments “did not prevent either of us from being rational.” (While the Department of Energy did not respond to a request for comment for this article, a spokesman confirmed the broad outlines of Salehi’s account of events for Science.)

While acknowledging that both parties represented their own national interests, Stone says he finds the general sentiment credible. “Thanks to their scientific track records and their personalities, they respected each other and could ultimately reach compromises on a number of sensitive technical issues—compromises that had eluded the political negotiators.”

This idea—that the language of science can achieve what political negotiation cannot—comes up again and again in conversations with advocates for science diplomacy. As Sandra Butcher, the Executive Director of the Pugwash Conferences, an international group devoted to bringing a scientific perspective to global problems, said, “scientists can show technical solutions are possible if the political will is present.”

The physicist Rush Holt, the CEO of the American Association for the Advancement of Science and a former seven-term Congressman for New Jersey, agrees that scientists’ participation was critical. Aside from the closed-door meetings between Moniz and Salehi, Holt points to the work of the broader scientific community in suggesting alternative solutions. “In the months leading up to the agreement,” he says, “unofficial American scientists were proposing in print and in private discussions with Iranian and American leaders specific proposals, such as changing the core of the plutonium-generating reactor and limiting not only the number of uranium-enriching centrifuges but a combination of centrifuges and uranium supply.” Both of these proposals made it into the final agreement.

Of course, scientists are people too, and not necessarily people with the political savvy necessary to conduct international negotiations. “It would be naïve,” Butcher says, “to think that scientists themselves are personally neutral.” Moreover, she notes, scientists from different countries often have “varying levels of independence” and access to different levels of classified information.

On the whole, though, science diplomacy has few contemporary detractors. Those who oppose the Iran deal oppose its politics, not the role of scientists in making it happen. As Stone puts it, “It's amazing how bona-fide scientists, no matter where they are—Pasadena or Pyongyang, Toledo or Tehran—can come together and bond over a common cause.”

Stone’s reference to Pyongyang is not coincidental: With the U.S.’s relationship with Iran set to improve, advocates for science diplomacy are wondering what the approach can accomplish in North Korea. Vaughan Turekian, the State Department’s new science advisor, has participated in several events sponsored by the US-DPRK Science Engagement Consortium, a group co-founded in 2007 by Linda Staheli to promote a better relationship with the secretive North Korean regime. Whether science can accomplish more than attempts at informal engagement remains to be seen, but it surely can’t be worse than, say, Dennis Rodman’s attempts at hoops diplomacy.